Process for treating a powdered fat-containing milk product

ABSTRACT

The reconstitution properties in cold water are improved of a powdered fat-containing milk product, especially whole milk powder, by applying a coating of lecithin, possibly dissolved in a fat. The quantity of lecithin and the quantity as well as the melting characteristic of the possible fat which is applied, are proportioned in dependence of the quantity and the melting characteristic of free surface fat present on the milk product prior to the treatment, as well as in dependence of the specific surface of the milk product. Hereby the quantity of lecithin and possible added fat plus the free surface fat present prior to the treatment is kept within specified limits, and the ratio between lecithin and that part of the free surface fat present before the treatment which is liquid at ambient temperature plus that part of the possibly applied fat which is liquid at ambient temperature is also kept within specified limits, and further a specified minimum thickness is obtained of the liquid fraction present on the surface of the product after the treatment. The treated product has excellent reconstitution properties in cold water.

States Patent [191 Pisecky et al.

[ PROCESS FOR TREATING A POWDERED FAT-CONTAINING MILK PRODUCT [75]Inventors: Jan Pisecky; Vagn Westergaard,

both of Tastrup, Denmark [73] Assignee: Aktieselskabet Niro Atomizer,

Soborg, Denmark [22] Filed: Sept. 22, 1971 [21] Appl. No.: 182,799

[30] Foreign Application Priority Data Sept. 25, 1970 Denmark 4920 [56]References Cited UNITED STATES PATENTS 3,164,473 1/1965 Shields et a199/56 3,120,438 2/1964 Mclntre et al. 99/203 FOREIGN PATENTS ORAPPLICATIONS 463,394 2/1950 Canada 99/56 [4 Nov. 20, 1973 PrimaryExaminer-S. Leon Bashore Assistant Examinerl(enneth M. SchorAtt0rneyRichard C. Sughrue et al.

[5 7] ABSTRACT The reconstitution properties in cold water are improvedof a powdered fat-containing milk product, especially whole milk powder,by applying a coating of lecithin, possibly dissolved in a fat. Thequantity of lecithin and the quantity as well as the meltingcharacteristic of the possible fat which is applied, are proportioned independence of the quantity and the melting characteristic of freesurface fat present on the milk product prior to the treatment, as wellas in dependence of the specific surface of the milk product. Hereby thequantity of lecithin and possible added fat plus the free surface fatpresent prior to the treatment is kept within specified limits, and theratio between lecithin and that part of the free surface fat presentbefore the treatment which is liquid at ambient temperature plus thatpart of the possibly applied fat which is liquid at ambient temperatureis also kept within specified limits, and further a specified minimumthickness is obtained of the liquid fraction present on the surface ofthe product after the treatment. The treated product has excellentreconstitution properties in cold water.

4 Claims, 3 Drawing Figures Patented Nov. 20, 1973. 3,773,519

3 Sheets-Sheet l Patented Nov. 20, 1973 3,773,519

3 Sheets-Sheet 2 Patented Nov. 20, 1973 3,773,519

3 Sheets-Sheet S PROCESS FOR TREATING A POWDERED FAT-CONTAINING MILKPRODUCT The present invention relates to a process for treating apowdered fat-containing milk product in order to enhance itsreconstitution properties (more particularly wettability anddispersibility) in cold water, in which a coating of lecithin, possiblydissolved in a fat, is applied to powder agglomerates having a particlesize of more than 100 p.

Fat-containing powdered milk products, such as whole milk powder,powdered compositions for the production of ice cream, powderedcompositions for the feeding of infants of powdered calf feedcompositions, cocoa mixtures containing milk powder, have, on thesurface of the individual particles, a layer of fat which is termed freefat and the quantity of which may be determined by extraction with asolvent that is immiscible with water such as tetrachloromethane. Thequantity of the free fat present on the surfaces of the particles isdetermined, besides by the properties of the starting material employedin the production of the powder, by the conditions prevailing in theproduction and during the handling of the powder, since a gentleprocessing in the course of the production of the powder and subsequenthandling resultsin the quantity of free fat present on the surfacebecoming very small, while a less gentle treatment has the result thatan increased part of the fat content of the product is going to be foundin the form of free surface fat.

The free fat present on the surface of the individual particles andparticle agglomerates affects the reconstitution properties of thepowdered milk product that means ability of, by the absorption of water,forming a liquid product in which the individual particles are evenlydispersed or emulsified in the water, and in particular, affects itsability of being rapidly dispersed in water, which is the essentialprecondition for the subsequent re-dissolution and emulsification.

This means that, for instance, in the preparation of whole milk fromwhole milk powder having a high free fat content, a relatively intensiveor prolonged mechanical whipping is required in order to achieve anadequate distribution of the powder in the water.

The reason for this is that the free fat reduces the wettability of thepowder and may, moreover, result in an agglutination of the particlesand agglomerates which prevents the dispersion of same in the water.

In order to eliminate these drawbacks, it has been proposed to apply acoating of lecithin to the powdered product, which lecithin may possiblybe dissolved in a fat. Furthermore, based on the recognition that is isespecially that part of the free surface fat of the powder which ispresent in a solid state at ambient temperature which has an impairingeffect on the reconstitution properties of the powder in cold water, ithas been suggested to modify the production method for whole milk powderin such a way, that prior to the drying of the milk concentrate, aseparation and fractionation of a part of the butterfat of the milk becarried out (cf. British Pat. specification No. 1,005,825). Thehigh-melting fraction hereof is recycled to the milk concentrate beforesame is spray-dried, while the low-melting fraction is applied as acoating on the dried powder. Hereby it is achieved that thewater-repellent effect of the solid part of the free surface issuppressed. It has also been proposed to add lecithin to the said liquidbutterfat fraction prior to same being applied to the powder.

The separation and fractionation of a part of the butterfat from themilk does, however, result in a considerable complication in andincrease in cost of the entire processing when producing milk powder,and an apparatus is required which is not normally available in plantsproducing milk products.

It has now been found that it is possible to obtain a powderedfat-containing milk product of the kind dealt with possessingparticularly good reconstitution properties in cold water, by ensuringthat the content of free surface fat of the product lies within quitespecific limits and that, in addition, the surface of the productcontains lecithin in a specific quantity which is dependent upon thequantity of that part of the fat in the surface of the product which isliquid at ambient temperature. The process according to the inventionis, in conformity herewith, characteristic in that the quantity oflecithin and the quantity as well as the melting characteristic of thefat possibly applied, are proportioned in such a way that the quantitythereof, together with the free surface fat present on the milk productprior to the treatment, constitutes l3 percent by weight of the treatedproduct, and in that the quantity of lecithin amounts to 15-25 percentby weight calculated on that part of the free surface fat present priorto the treatment which is liquid at ambient temperature, plus that partof the possibly applied fat which is liquid at ambient temperature,whereby the quantity applied is, in addition, fixed due regard being hadto the specific surface of the milk product, so that a calculatedthickness of more than 0.l u is obtained for the liquid fraction presenton the surface, the temperature of the product being at least 35 C,preferably approximately 50 C, during the treatment, and/or the productis heated to such a temperature after the treatment.

This minimum temperature is fixed to ensure sufficient equalization ofthe coating on the powder agglomerates.

A preferred embodiment of the process according to the invention ischaracteristic in that the lecithin is applied dissolved in a melted fathaving the same composition as the fat forming part of the powderedproduct. This results in the composition of the powder not being changedin any way which would contravene legal provisions and, moreover, inrendering superfluous the complicated fractionation of the fat in afraction having a relatively high and a fraction having a relatively lowmelting point.

When, for instance, treating whole milk powder according to thispreferred embodiment of the process, the lecithin will thus be applieddissolved in melted unfractionated butterfat. Dependent upon the time ofthe year, unfractionated butterfat contains approximately 40 percent ofa fraction which is liquid at ambient temperature, while the remaining60 percent are constituted of a fraction, the melting point of whichlies about ambient temperature. The use of such unfractionated butterfatin the process according to the invention ensures the surface of thepowder being coated with an adequate quantity of lecithin-containing fatwhich is liquid at ambient temperature in order to obtain satisfactoryreconstitution properties since the hydrophobic effect of the solidfraction of the fat, contrary to what could have been expected, underthe given circumstances affects the reconstitution properties of theproduct to only a very slight degree.

The quantities of lecithin and of a possible fat are selected within thestated intervals in dependence upon the degree of agglomeration of thepowder to be treated, in that a product which is agglomerated to aparticularly high degree requires relatively small additions on accountof the fact that such a product has a comparatively small surface area.The best results are obtained with a calculated thickness of the surfacelayer of 0.1 0.3 t, for which reason it is expedient to measure orcompute the size of the surface of the agglomerated powder with a viewto determining the quantities of fat and lecithin which render theobtention of this thickness possible. In the treatment of whole milkpowder intended for human consumption, in order not to impair theflavour, 0.4 percent of lecithin at the most should be used, calculatedon the weight of the powder.

In the production of the product to be treated, so gentle a method willhave to be used that the quantity of free fat does not exceed 3 percentby weight. In connection with whole milk powder, this means that boththe drying and the agglomeration have to be effected by means of gentlemethods without any violent thermal or mechanical influences beingemployed.

As will be understood from the above the raw material for the processaccording to the invention is a powdered fat-containing milk producthaving a particle size of more than 100 microns. The material may bemanufactured by any known method e.g. by a modified spray drying processor other methods for the manufacture of agglomerated fat-containing milkpowders.

The lecithin treatment according to the invention may be carried out ina plant which is in direct connection with the spray drying plant.Alternatively, the lecithin treatment may be carried out on powder whichis manufactured in a separate plant and which has possibly been subjectto prolonged storage and/or transportation.

The invention will now be described in more detail with reference to thedrawings.

FIG. 1 shows schematically by way of example a known plant for themanufacture of whole milk powder in a quality which will be suitable fortreatment according to the invention.

FIG. 2 shows schematically a preferred embodiment ofa complete plantcomprising a plant for the manufacture of spray dried whole milk powderidentical with the plant shown in FIG. 1 this drying plant being indirect connection with a plant for the subsequent lecithin treatment.

FIG. 3 shows schematically another embodiment of a plant for lecithintreatment of powder according to the invention. The powder for theprocess may be manufactured a considerable length of time before thetreatment in the plant shown, and it may be manufactured at a distancefrom and transported to the treatment plant.

In FIG. 1 drying gas for a spray dryer 1 is supplied by a fan 2 fromwhich the gas passes through a heater 3 and a line 4 to an air disperser5 at the top of the spray dryer 1.

Whole milk is concentrated in an evaporater (not shown) and pumped bymeans of a pump 6 through a line 7 to a rotary atomizer 8 at the top ofthe spray dryer 1.

The spray dried milk powder containing some moisture leaves the bottomof the spray dryer through an outlet 9 and falls into a fluidized bedapparatus 10 which is divided into three treatment zones 11, 12 and 13respectively. Each zone is connected with filters 14,

15 and 16 respectively, fans l7, l8 and 19 respectively, heaters 20, 21and 22 respectively and lines 23, 24 and 25 for the supply of drying gasor air at ambient temperature.

The milk powder leaves the fluidized bed apparatus 10 through an outlet26 and falls direct into a sieve 27 which may be of the horizontallyvibrating type. In the sieve the product is classified into twofractions, the coarse fraction being the final product leaves throughoutlet 28 and the fine fraction being recycled as described later,leaves through outlet 29.

The drying gas from the sprayer dryer 1 contains some fine particles ofthe powdered product and it is led through line 30 to a cyclone 31 wherethe fine particles are separated and transferred through a rotary valveto a line 32.

The drying gas leaves the cyclone 31 through a fan 33 and a chimney 34.Fine particles which are blown off in the fluidized bed apparatus 10 arealso trans ferred to the line 32. A fan 35 draws air through a filter 36and the line 32 for pneumatic transport of the fines to a cyclone 37.The fines that are separated from the gas leave the cyclone through arotary valve 38 and is led through line 39 to another pneumatictransport line 40.

The air from the cyclone 37 passes through the fan 35 to the chimney 34.

A fan 41 and the line provides pneumatic transport of the fines from thesieve 27 and from the cyclone 37. The fines are introduced in a knownmanner into the zone of atomization of the spray dryer.

The plant shown in FIG. 2 is quite similar to the oen shown in FIG. 1but a lecithin treatment chamber 42 is inserted between the fluidizingapparatus 10 and the sieve 27.

Lecithin solution is pumped from a tank 43 by means of a pump 44 througha flow meter 45 and line 46 to a two fluid nozzle 47 placed centrally inthe treatment chamber 42. The lecithin solution is atomized by means ofcompressed gas coming through line 48 to the nozzle 47.

The milk powder leaving the fluidized bed apparatus 10 falls dispersedin air around the nozzle and becomes coated with the lecithin solution.From the treatment chamber 42 the powder falls direct down into thesieve 27 where some equalization of the lecithin solution on the powdertakes place. The product is classified in two fractions and the coarsefraction representing the final product is packed in suitablecontainers.

In the plant shown in FIG. 3 powder from a silo 49 equipped with arotary valve 50 is fed through a line 51 to a fluidized bed apparatus 52to which warm air is introduced through a line 53 by means of a filter54 a fan 55 and a heater 56.

From the fluidized bed apparatus 52 the powder is treated in a chamber42 quite similar to the one shown in FIG. 2.

After the lecithin treatment the powder falls direct into anotherfluidized bed apparatus 57 (where equalization of the coating takesplace) to which warm air is introduced through a line 58 by means of afilter 59 a fan 60 and a heater 61.

The powder leaves the fluidized bed apparatus 57 as the final product.

Fines from the two fluid bed apparatus 52 and 57, respectively, aretransferred through lines 62 and 63 to a cyclone 64 where they areseparated from the air. The air is exhausted by means of a fan 65 andthe fines leave the cyclone through a rotary valve 66.

The process according to the invention is illustrated in greater detailwith the aid of the following examples.

EXAMPLE 1 In the course of this example, a total of five tests relatingto the treatment of whole milk powder was carried out using a plant asshown in FIG. 2. This whole milk powder was produced from whole milkhaving a fat content of 3.3 percent by weight and a content of non-fattysolids of 9.4 percent which, prior to spray drying, had been heated to86C and evaporated to a total solids content of 44 percent by weight.This concentrate was spray-dried by utilizing a spray drier of the NiroAtomizer make and the powder obtained hereby received finishingtreatment in a drier having u e s in threeiuqssssiy zonesend n mmediatconnection with the spray drying plant. In the spray drier, an entrytemperature of the drying gas of 182 C was used and a dischargetemperature of the gas of 87 C. The moisture content of the powder was5.2 percent when being removed from the spray drying plant, 4.4 percentat the end of the first drying zone and 2.8 percent when leaving thesecond drying zone. After having passed through the third zone thetemperature of the powder was over 35 C, and the moisture content was2.6 percent and subsequently a solution of lecithin in butterfat wassprayed on to the whole milk powder.

This spraying operation took place by the powder being allowed to dropdown dispersed in air around a two-fluid nozzle where the solution wasatomized by means of compressed air. The first five tests were carriedout in such a way that the same amount of lecithin was dosed in all thecases, while the quantity of butterfat and its composition were varied.In tests 1 4 unfractionated butterfat was used, 'rhi'it' say butterfat,of which 40 percent was liquid at ambient temperature, whereas in testNo. 5, a butterfat fraction was used instead which was liquid at ambienttemperature.

The details of the tests and the results obtained appear from the tableprovided below. It appears from this table that by carrying out thetreatment by using the process according to the invention as was done intest No. 4, reconstitution properties are obtained which are,substantially, just as good as those obtained when treating the powderaccording to the known, but by far more complicated process which isused in test No. 5, in which, preceding the treatment, a fractionationof the butterfat supplied is carried out.

It is remarked that the calculations in the table are carried out basedon the assumption that also the free surface fat present on theuntreated powder, by about 40 percent, consists of a fraction which isliquid at ambient temperature.

The whole milk powder which was treated in this example had a relativelylow free surface fat content and a relatively large area per unit ofweight, for which reason it was necessary to supply a comparativelylarge amount of butterfat for meeting the demands made by the processaccording to the invention.

The reason why satisfactory reconstitution properties were not obtainedin test No. 3 was due to the fact that the liquid fraction in thesurface layer was only just sufficient for forming a surface layerhaving a computed thickness of 0.1 t, which was not wholly adequate foreffectively enhancing the wettability of the powder.

EXAMPLE 2 In this example, whole milk powder was treated, which wasproduced from whole milk having a fat content of 3.25 percent by weightand a non-fatty solids content of 8.90 percent by weight, which wholemilk, prior to the spray drying, was heated to C and evaporated to 50.8percent by weight of total solids. This concentrate was spray-dried andsubjected to a finishing drying process in the same apparatus as the oneemployed in Example I, wherein for the spray drying plant an entrytemperature of the drying gas of 187 C and a discharge temperature of 79C were used. The moisture contents obtained were as follows. Whenleaving the spray drying apparatus, it was 5.7 percent, when leaving thefirst fluid bed zone it was 4.5 percent and when leaving the secondfluid bed zone it was 2.3 percent and after the third fluid bed zone 2.2percent. The temperature of the powder leaving the third zone was higherthan 35 C.

The powder was treated by utilizing the process according to theinvention in a similar manner as described in Example 1. Thecharacteristics of the powder and of the treatment used are detailed inthe table below.

It is seen from the table that the higher content of free surface fat inthe untreated powder, which surface TABLE Example 1.-Test number 00Example l 3 4 5 2 1 Free surface fat in untreated powder, percent byWeight 0.8 O. 8 0. 8 0. 8 0.8 2. 1 2 Lecithin added, percent by weighton powder..." 0. 2 0. 2 0.2 0.2 0. 2 0.2 3 Butterlat added, percent byweight on powder. 0. 2 0.5 1.0 2.0 I 0.8 0. 2

4 Liquid fraction 01' added butterfat, percent by weight on powder 0. 080. 2 0. 4 0.8 0. 8 0. 08 5 Entire surface layer, percent by weight onpowder 2 l. 2 1. 5 2. 0 3. 0 1. 8 2. 5 6 Liquid fraction of surfacelayer, percent by weight on powder t. 0. 6 0.72 0. 92 1. 32 1. 32 1. 127 Lecithin, percent by weight on entire surface layer 16. 7 13. 3 10. 06. 7 11. 1 8, 0 8 Lecithin, percent by weight on liquid fraction ofsurface layer..- 33. 3 27. 8 21. 7 15. 1 15. 1 17. 8 9 Surface area ofpowder mfl/lOO g. 9- 8 9. 8 9. 8 9. 8 9. 8 5. 7 10 Liquid fraction insurface layer per area unit surface, g./m. 0. 061 0. 073 0. 094 O. 0.135 0. 197 1 1 Thickness of liquid surface fraction p 0. 065 0. 078 0.100 0. 144 0. 144 0. 209

5 min. 5 min. 5 min. 20 sec. 17 sec. 6 sec 12 Wettabillty, see/13 g.powder 6 1 The butterfat used in test 5 was only the fraction liquid atambient temperature.

2 Calculated as 1+2+3. 1 Calculated as 1 %+2+4.

4 Determined by measuring the permeability to air. 5 Calculated on thebasis of a density of 0.948 g./em. 0 Determined by careful, standardizedpouring of 13 g. powder on to the quiescent surface of 100 ml. water andby measuring the time which elapscs before the powder has sunk below thesurface of the water.

fat has hitherto been regarded as being deleterious to thereconstitution properties of the powder, by means of the treatment usedin the process according to the invention and by employing a relativelysmall amount of added butter-fat, renders possible the obtention of asurface layer having a suitable thickness of the liquid surface fractionand a suitable concentration of lecithin so that the reconstitutionproperties of the powder become particularly satisfactory.

EXAMPLE 3 In this example whole milk powder was produced in a plant asshown in FIG. 1 using the same operating conditions as described for thedrying in example 2 except that the heater 22 was not used, the moisturecontent of the powder when leaving the fluidized bed apparatus 10consequently was 2.7 percent instead of 2.2 percent.

This powder was then filled into 500 kg containers which were shipped toa another factory in another country at a considerable geographicdistance from the first factory.

17 days after the manufacture, the milk powder was treated according tothe invention in an apparatus as shown in FIG. 3. The temperature of thegas entering the fluidized bed apparatus 52 and 57 were 59C and 43 Crespectively. Which means that the temperature conditions of the presentprocess were fulfilled. In the treatment chamber 42 the powder wastreated utilizing the process according to the invention in a similarmanner as described in example 1.

The powder collected in the cyclone was packed in paper bags. Thequality of this powder corresponded to ordinary non-agglomerated wholemilk powder and the quantity was 5.5 percent of the total production.

The final product leaving the fluidized bed apparatus 57 was collectedin 200 kg containers and packed in one-half lb tins using known nitrogenpacking technique.

N significant difference between the properties of the powder and thepowder of example 2 could be observed. The wettability of the powder wasmeasured at sec. and the dispersibility was visually evaluated to besomewhat better than the powder of example 2.

Even though the process according to the invention is described here inconnection with the treatment of milk products, it will be obvious tothe person skilled in the art that it may be employed for the treatmentof other fat-containing powdered products to which it is desired toimpart such a wettability in cold water that it will be easier to mixthem in same. As examples of such products, compositions containingcocoa and milk powder may be quoted.

What we claim is:

1. A process for treating a powdered fat-containing milk product inorder to enhance its reconstitution properties in cold water, comprisingapplying a coating of lecithin dissolved in a fat to powder agglomeratesof said milk product having a particle size of more than microns,whereby the quantity of lecithin and the quantity of fat which are to beapplied satisfy the following inequalities:

l$a+b+c+d+e 3,

15 100 e/a+c) s 25,and

the numerical value of the sum of a c e than the numerical value of 10timesf wherein a is the percent by weight of free surface fat which ispresent prior to the treatment and which is liquid at ambienttemperature,

b is the percent by weight of free surface fat which is present prior tothe treatment and which is solid at ambient temperature,

c is the percent by weight of fat to be applied which is liquid atambient temperature,

d is the percent of weight of fat to be applied which is solid atambient temperature,

e is the percent by weight of lecithin to be applied,

and

fis the specific surface area in cm /IOO g powder, the temperature ofthe product being at least 35 C during the treatment or the productbeing heated to a temperature of at least 35 C after the treatment, saidpercents by weight being based on the weight of the powder prior to saidtreatment.

2. A process as claimed in claim 1, wherein the lecithin is applieddissolved in a melted fat having the same composition as the fat formingpart of the powdered product.

3. A process as claimed in claim 1, wherein the temperature isapproximately 50 C.

4. The product produced by the process of claim 1.

2. A process as claimed in claim 1, wherein the lecithin is applieddissolved in a melted fat having the same composition as the fat formingpart of the powdered product.
 3. A process as claimed in claim 1,wherein the temperature is approximately 50* C.
 4. The product producedby the process of claim 1.